1. Field of the Invention
The present invention relates to a sensing apparatus including a microprocessor having an A/D converting function of digital-converting an analog electric quantity supplied to an A/D conversion port to take in a conversion result, and a plurality of electrical elements that are connected with the microprocessor and generate analog electric quantities.
2. Description of the Related Art
In recent years, a microprocessor (an IC) having an A/D converting function has been developed. This type of microprocessor digital-converts an analog electric quantity (a voltage) given to an A/D conversion port thereof and takes in a conversion result. For example, the microprocessor is used when temperature information (an analog voltage value) detected by a thermistor (a temperature sensing element) is inputted to the microprocessor and the microprocessor performs various kinds of controls based on this temperature information.
As a specific example, FIG. 3 shows a charge/discharge controller that detects terminal voltages V1, V2, and V3 and a charge/discharge current I of a plurality of battery cells constituting a secondary battery BAT to control charge/discharge of the secondary battery BAT. In this charge/discharge controller, a battery temperature of each battery cell is detected by using a thermistor T, and the detected temperature information is used to perform correction of battery characteristics when executing the charge/discharge control or an operation of a protection circuit for the secondary battery BAT. As a main control section in such a charge/discharge controller, the above-explained microprocessor is used.
It is to be noted that, in this charge/discharge controller, temperatures of various kinds of electronic components mounted on a printed circuit board are detected and operation characteristics or operation compensating temperatures of the electronic components, e.g., a charge/discharge control transistor or a current detection resistor are also monitored in accordance with the detected temperatures.
Meanwhile, in a case where temperature information (analog voltage values) detected by each of a plurality of thermistors (temperature sensing elements) is inputted to the microprocessor, it is general that the plurality of thermistors (the temperature sensing elements) are respectively connected with a plurality of A/D conversion ports of the microprocessor as shown in FIG. 4. Specifically, fixed resistors R1 and R2 are respectively connected with two thermistors T1 and T2 in series, and a constant direct-current voltage V outputted from an output port of an analog circuit A is applied to each of these series circuits, thereby driving the respective thermistors T1 and T2. Further, voltages (output voltages from the thermistors) divided by the thermistors T1 and T2 whose resistance values vary depending on a temperature and the fixed resistors R1 and R2 are respectively inputted to two A/D conversion ports of a microprocessor M through filter circuits F1 and F2.
However, when taking temperature information detected by each of the plurality of thermistors T into the microprocessor M in this manner, the plurality of fixed resistors R and filter circuits F must be respectively provided in accordance with the number of the thermistors T, and the number of the A/D conversion ports of the microprocessor M must be also increased. Therefore, the structure is compulsively complicated.